docs: upgrade Keptn to Helm from a manifest installation

[odubajDT]

Fixes: #1176

[netlify]

✅ Deploy Preview for keptn-lifecycle-toolkit ready!

Name	Link
🔨 Latest commit	a9e660f
🔍 Latest deploy log	https://app.netlify.com/sites/keptn-lifecycle-toolkit/deploys/652e4bc6a4a07f00089684bc
😎 Deploy Preview	https://deploy-preview-2270--keptn-lifecycle-toolkit.netlify.app/docs/install/upgrade
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[thisthat]

I think the best way to support this would be providing a CRD-less manifest for each old installation. This way it could simply be: kubectl delete -f keptn-vX.Y.Z-crdless.yaml; helm install ...
This way the CRD definition will live and the CR won't be lost, but all the rest is cleaned up. I don't know, however, how Helm handles the CRD again since are already there 🤔

[RealAnna]

I think the best way to support this would be providing a CRD-less manifest for each old installation. This way it could simply be: kubectl delete -f keptn-vX.Y.Z-crdless.yaml; helm install ... This way the CRD definition will live and the CR won't be lost, but all the rest is cleaned up. I don't know, however, how Helm handles the CRD again since are already there 🤔

If we provide a CRD-less chart than users need to update CRDs manually via manifest, and they are stuck forever in this 😢

[StackScribe]

I'm thinking that we should pull the backup info into its own page in the "Operate" section then link to that from here. But let's merge this PR first then I can do that in a separate PR.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
39 Code Smells

No Coverage information
0.1% Duplication